ISS mouse experiment tests how the body adapts to living on the Moon

Astronauts living on the International Space Station (ISS) spend hours working out every day just to avoid losing serious muscle mass and bone density in microgravity. But will such precautions be needed to live on worlds that are simply lower in gravity than Earth, like the Moon and Mars? And what effect would such gravity have on growing children? These questions are almost entirely unanswered by science, but they’re vital for humanity’s aims to build permanent settlements off-world.

Now Japan has taken a first step toward answering some of these questions thanks to a new instrument in their KIBO module on the ISS. Called MARS – Multiple Artificial-gravity Research System – it can spin to produce gravity at a variety of levels. Scientists have used it to raise mice in microgravity, artificial Earth gravity, and artificial lunar gravity. Then, they compared the mice to those raised in a similar habitat on the ground in true Earth gravity.

Mice in Space!

The experimental mice were reared in space for a month before returning to Earth for study. All the mice survived their time on station and the trip back to the ground. Upon returning to Earth, the mice were dissected to check their growth rates and internal organs.

The first round of experiments, back in 2017, compared the mice raised in artificial Earth gravity and microgravity to those raised on Earth. Scientists found that the ones raised with gravity – real or artificial – seemed to do fine. But the mice raised in microgravity suffered from loss of bone density and muscle mass compared to the other mice.

That’s pretty normal. Experiments on both mice and humans have proven this over more than half a century of spaceflight. But it was still helpful to prove that mice raised in artificial gravity could do as well as those raised with the real deal on the ground.